1. Field of the Invention
The present disclosure relates to a method and system for obtaining the degradation of a battery, and a secondary battery operation system based on the method and system.
2. Description of the Related Art
Energy conservation and environment protection have now drawn attentions from various industries and businesses. Many countries focus on vehicles using new energy sources as the development of automobile industry. Compared with conventional vehicles with internal combustion engines, vehicles using new energy sources have advantages in saving traditional resources, protecting environment and the like. EVs (electric vehicles) are one of the choices. However, it is difficult to put EVs into market due to low energy density and long charging time for batteries. For example, a lithium ion battery currently has an energy density of about 150 wh/kg, while the energy density for gasoline is 10000 to 12000 wh/kg. Further, it is difficult to charge a battery to fullness in a short time. Currently, it usually takes about 3 to 5 hours to charge a battery to its full capacity. Most of users can hardly accept such long charging process, unless this charging is carried out in their houses. Even a quick non-saturated charging process, it may take about 30 minutes. A battery is usually expensive. The price of a lithium ion battery with unit capacity is around 0.5 to 1.00 dollar/wh. Battery cost for a car will be from thousand to tens of thousand dollars. There is also security requirement for EV battery. Since EV battery has an energy storing capacity much larger than a built-in battery for a mobile device, and also a higher risk of being impacted, squeezed, or suffering high temperature in some extreme conditions, the battery has higher security requirement, and this further adds the cost of EV battery.
The above problems for batteries may be ultimately solved with progress of battery technology. However, in a short period, it is still difficult to address the problems, such as slow charging process and higher cost.
In view of the problems like long charging time and high cost, some BOMs (battery operation models) have been introduced. One of the BOMs is replacing batteries instead of charging them. It may take only one or two minutes to replace a battery pack. Another BOM associated with battery replacement is battery rental. An owner of an EV does not have to purchase expensive batteries. Instead, he or she may rent EV battery, and this may considerably reduce the initial cost for buying an EV. A further BOM is a life-time efficient utilization of a battery, and indirectly reduces cost during use of the battery. For example, when an EV battery degrades in performance and thus its capacity decreased to a certain ratio (e.g., 80%) of its rated capacity, this battery may be used as accumulator battery for household or business facilities. The battery may be recycled if the battery capacity further decreases to a certain level. A yet further model is to circulate or exchange EV batteries among automobile owners, and thus to reduce cost for maintaining or using the battery.
A method for obtaining degradation or residual life time of a battery is to obtain the degradation through battery charge and discharge experiments. This method requires full charge of a battery and then rapid discharge. It takes a long time and detrimental to the battery. Thus, this method is not suitable for battery operation.
PCT International publication No. WO 2006/090636 A1 discloses the battery exchange scheme which is primarily applied to mobile terminals.
Japan patent laid-open publication No. JP 2007-074891 A discloses conventional methods for estimating degradation of an EV battery take into account influences on the degradation from different vehicle models (vehicle weight, equipments of electric devices, such as in-vehicle air condition), different road conditions, and external environment.